1. Field of the Invention
The present invention relates to the continuous polymerization of olefin polymers with long chain branching. In particular, the present invention relates to the continuous polymerization of ethylene and a diene to yield partly crystalline polymers containing long chain branching.
2. Prior Art
The coordination catalyst polymerization of polymers of ethylene and of copolymers of ethylene and mono-olefins is well known. Such polymers have many desirable physical properties and they have been used in a wide range of commercial applications especially as film and as moulded articles. However, it has been found that these polymers have rheological characteristics which result in process difficulties during the melt processing of these resins. One critical rheological deficiency is the low activation energy of viscous flow, i.e., the melt viscosity of the resin shows only relatively minor changes over the temperature range of 150.degree.-300.degree.C. normally used in commercial melt processing operations. Because of this low activation energy of viscous flow it may be necessary to use a polymer of lower molecular weight than is desirable in terms of the properties of the fabricated article in order to obtain the required degree of melt flow during the processing of the resin.
In the preparation of sulphur-curable polymers, ethylene may be polymerized with a diene. The preferred dienes have double bonds of unequal reactivity so that the polymer produced has residual unsaturation which may be subsequently used in the cross-linking of the resin. The preparation of such polymers is described in U.S. Pat. No. 2,933,480 which issued to W. F. Gresham and M. Hunt on Apr. 19, 1960 and U.S. Pat. No. 3,211,709 which issued to S. Adamek et al. on Oct. 12, 1965.
The preparation of cross-linkable polymers of ethylene and bicyclo-(2,2,1)-2,5-heptadiene is described in Canadian Pat. No. 607,108 which issued to G. S. Stamatoff on Oct. 18, 1960.
It is an object of the present invention to provide an olefin polymer with a higher activation energy of viscous flow.
It is a further object of this invention to provide an olefin polymer with a higher activation energy of viscous flow and having low residual carbon-carbon double bound unsaturation.
It has been found that the activation energy of viscous flow of polymers of ethylene may be increased by introducing long chain branching into the polymer. It has been found that the long chain branching in the polymer may be obtained by polymerizing ethylene with a non-conjugated diene in which the carbon-carbon double bonds are of essentially equal reactivity and capable of reaction with a coordination catalyst under the reaction conditions.